1. Field of the Invention
The present invention relates to deep well pumping devices and more particularly to a counterbalancing arrangement useful therewith.
2. Description of the Prior Art
As the deposits of oil are used up, extraction from less productive fields become an economically feasible operation. Characteristically, drilling in less productive fields is associated with decreases in the efficiency to a point where the extraction process itself quickly dominates the competitive advantage that a particular producer engages in. Heretofore most of the prior art pumping mechanisms attempted to convert from rotary input into a reciprocal input at the well pump. To achieve this various counterbalances were often necessary. Most frequently, the counterbalancing was arranged to augment the operation of a walking beam pumping device. These devices require constant application of power and the power consumption therefore varies over the load variations incident in the pumping stroke. This variation in power input has been recognized as a major cause of inefficienty, the power plant often operating outside of the optimum band as various load peaks are encountered.
In alternative prior art devices the use of electric motor switching has been practiced, and again on each reciprocating cycle a full reversal of motor input is made. This technique encounters the necessary starting transients in each stroke cycle which in the case of electrical power entails large periodic current draws. Similarly, in the case of mechanical motors, the switching arrangement entails complicated clutching and gearing sequences which once more are a source of great power loss.
Thus, in each instance, less than optimum use of the power input is found. In the more recent developments, a device known as the Alpha I, sold by the Bethlehem Steel Corporation, utilizes an eccentrically wound cable system, one eccentric feeding the well pump while the other eccentric being tied to the counter balance. By virtue of this arrangement, an oscillatory system is made out which, in the absence of the pumping and friction losses will maintain oscillations indefinitely. Thus, the only added input is that required to overcome the fluid friction and the pumping heads, i.e., work directly associated with the production of oil. This same Alpha One system, in order to overcome the start-up transient losses set out above, also include switching logic whereby the electric motor is switched on during the times as when the stroke of the pump is at substantial velocity.
The wind up of cable, however, on an eccentric spool requires compound spool arrangements and consequently the angle of departure of the cable varies throughout the stroke. This inherent feature grossly reduces the life expectancy of the cable and furthermore adds friction to the system which must be compensated for by way of external power input. Thus, while the last mentioned pumping apparatus does provide great advantages in power utilization, certain features thereof may be improved for full mechanical optimization.